St.Hilda's is a small historic church set in a quiet valley near Thornton-le-Dale in the North York Moors. The valley is fringed by woodland, much of it part of Dalby Forest. A stream runs through the valley and there are a series of lakes - in all, the perfect place for bats.

It is not surprising that the church supports four species of bat - Common Pipistrelle, Whiskered, Natterer's and Brown long-eared. We have records of bats at the church dating back around 40 years, but in reality bats are likely to have used the church for hundreds of years. It is only in recent decades that modern technology has enabled more people to record them.

Until around 10 years ago the small congregation appear to have lived alongside the bats without complaint. Since then increasing concerns about the bats have been reported in the media.

The bats that are the cause of the complaints are the Natterer's and Brown long-eared bats. These species both roost in and fly within the church - the other bats mainly live between the layers of the roof and don't enter the main body of the building.

Brown long-eared bat Photo: copyright John Altringham

Whilst the Natterer's and Brown long-eared bats live within the roof and eaves of the church, many individuals of these two species flew within the building before emerging outside at dusk and to a lesser extent before returning to their roosts at dawn. The reasons why bats do this is not fully understood, but it is likely that it at least partly serves a social function for the colony. Such behaviour can be seen in other churches, barns and similar enclosed spaces where these species roost.

During these flights inside St Hilda's the bats deposited droppings and urine spots over the walls and furnishings inside the church. Claims were made that those using the church hadfallen ill and that the presence of bats constituted a health hazard, but there is no evidence that contact with bat droppings or bat urine carries any particular risk of disease in Britain.

Around 200 Natterer's bats use the building to raise their young. Bats are long-lived animals (often 15 years or more) and breed very slowly (only one baby a year). They are traditional in their behaviour, returning to the same place year after year. Churches are ideal for these species as they remain undisturbed for much of the time and provide numerous crevices in which bats roost, as well as the enclosed space for pre-emergence flight.

Since concerns about the bats were first raised, North Yorkshire Bat Group made a number of suggestions regarding the management of the bats in order to minimize the problems for the church. These range from temporarily covering surfaces between services to protect them and to make cleaning easier, regular cleaning of the church and the construction of a ceiling within the church to create a roof void so that the bats can fly without depositing droppings throughout the building. The Group even provided a team of volunteers a few years ago to clean the church and at one period English Nature provided funding for regular cleaning to be undertaken.

In 2011 Natural England granted a licence to allow the gap over the church door was traditionally the main access point for bats to be blocked.This did not adversely affect the bats which found alternative ways in and out of the building and, not surprisingly continue to fly inside. North Yorkshire Bat Group supported the granting of a licence as it was not expected to impact on the bats.

As part of their efforts to exclude the bats from the body of the church under licence, the church has carried out other mitigation measures. These include creating access points and installing heating in the roof of the lychgate and making alterations to a barn to the south in the hope of encouraging bats into these places. This mitigation was not suggested by the Bat Group and we consider both measures to be inappropriate given the ecological requirements of the species concerned.

In 2013 Natural England sponsored a research project to examine the ways in which bats used the church with a view to finding a suitable solution to the problem. This involved watching and listening for bats, radio-tracking of bats and ringing over several months. The research confirmed the importance of the church, especially for roosting Natterer's bats. Whilst a few additional small temporary roosts of bats were located during the project the church was the only significant roost within a large foraging area extending over 36 square kilometres of the surrounding countryside.

Following completion of the research a licence application was submitted to Natural England to permit the exclusion of bats from the inside of the church. North Yorkshire Bat Group expressed concerns because this would require the bats to alter their behaviour: for that reason such licences are not usually granted elsewhere as it can effectively mean the destruction of the roost. Natural England agreed to some amendments to the proposed scheme at St. Hilda's in order to include safeguards sould the worst happen.

We are pleased to report that early indications suggest that
the licensed works carried out by Natural England's contractor have
been successful in limiting the incursions of bats to the interior of St. Hilda's church at Ellerburn
whilst successfully retaining the roost in the building.

In 2014 Natterer's bats were present in roughly
similar numbers as in 2013 and Brown Long-eared bats which, in 2013 had left
the building early in the summer before breeding, stayed to breed. Other than the occasional incursion, bats
failed to find their way into the body of the church.

Of course the cold, wet spring and
summer of 2013 was a very different season to the hot and often dry summer of
2014 so this may have affected the results. Also, sometimes when bat roosts are altered bats do return in equal or
greater numbers afterwards only to disappear a year or two later. So, we are delighted that, in
this particular case, a solution appears to have been found, but we will
continue to closely follow the outcomes
over coming years before declaring it a total success.